The Principal/Primary Diagnosis is the condition established after study to have been chiefly
responsible for occasioning the admission of the patient to the hospital for care.
Since the Principal/Primary Diagnosis represents the reason for the patient's stay, it may not
necessarily have been the diagnosis which represented the greatest length of stay, the
greatest consumption of hospital resources, or the most life-threatening condition.
Since the Principal/Primary Diagnosis reflects clinical findings discovered during the patient's
stay, it may differ from Admitting Diagnosis.

Codes and Values:

Must have been a valid ICD-9-CM code excluding decimal points. To have been valid,
ICD-9-CM codes must have been entered at the most specific level to which they are
classified in the ICD-9-CM Tabular List. Three-digit codes further divided at the
four-digit level must have been entered using all four digits. Four-digit codes
further subclassified at the five-digit level must have been entered using all five
digits. Failure to enter all required digits in the diagnosis codes would have caused
the record to be rejected.

Must have been left justified and entered exactly as shown in the ICD-9-CM coding
reference, excluding the decimal point, and space filled.

Manifestation and Unacceptable Principal/Primary Diagnosis conditions as indicated
by the edit flag on the ICD-9-CM reference file were invalid.

Edits pertaining to ICD-9-CM codes are validated on the basis of the Discharge
Date (Data Element 6 & 7)
and Expected Principal Reimbursement
(Data Element 28) depending on conditions described in
Appendix N, which includes
age-specific and sex-specific diagnosis code conditions.

When the edit flag on the ICD-9-CM reference file indicates an "unacceptable
principal/primary diagnosis without a secondary diagnosis" an Other Diagnosis Code 1-14
(Data Element 69) must have
been reported.

Diagnosis codes reported in the range of 800.00-999.99 required the reporting
of a valid External Cause-of-Injury Code
(Data Element 77) unless
as an exception in Appendix N.

If the Neonate Birth Weight
(Data Element 21) was reported as less than 1500 grams, and the New York State
Patient Status (Data Element 22)
was reported as code "01" home, then the Length of Stay must have been greater than
10 days.